Determination of the permittivity of n-hexane/oil sands mixtures over the frequency range of 200 MHz to 10 GHz

摘要

Combined electromagnetic (EM) heating and solvent injection has been recently proposed to recover bitumen from oil sands due to its great environmental friendliness. The permittivity of oil sands with the presence of solvent is a crucial property for the design, evaluation, and optimization of this process. In this study, we use the open-ended coaxial probe method to measure the permittivity of oil sands over the frequency range of 200 MHz to 10 GHz. Results of the permittivity of the constituents of oil sands reveal that water is a major dielectric contributor; no relaxation phenomenon has been found for bitumen, sand, and n-hexane over the tested frequency range. Also, the results for the oil sands mixtures show that water content is crucial for the permittivity of oil sands; both the dielectric constant and loss factor are enhanced with an increasing water content. With the addition of n-hexane, the permittivity of bitumen slightly changes and fluctuates between the dielectric values of pure bitumen and n-hexane. As for the n-hexane/oil sands mixtures, the added n-hexane induces the asphaltene aggregation/flocculation, affecting the interaction between water and asphaltene and leading to an enhanced free water content in the oil sands. Consequently, the permittivity of oil sands significantly increases after n-hexane addition. Based on the experimental data, we evaluate the prediction accuracy of commonly used mixing models. A modified Lichtenecker-Rother model considering effective water saturation is proposed to accurately characterize the permittivity of n-hexane/oil sands mixtures. The obtained data and correlations can be useful when experimental data are missing.